1. Field of the Invention
This invention relates to beds of the type in which a patient is supported on a flexible web slung between two generally parallel shafts on to which the ends of the web are respectively wound. Thus the shafts can be turned in the same direction to transfer the web from one shaft to the other, enabling a patient lying on the web to be rolled over for repositioning thereon, or they can be turned in opposite directions to raise or lower the patient with respect to a conventional mattress or other support surface below the web.
2. Description of the Prior Art
When the web is of web or net form, as disclosed in U.K. Pat. Specification No. 1447163 and U.S. Pat. Specification No. 3905055, such a bed is particularly valuable in the prevention and treatment of bed sores. Beds of the type concerned are hereinafter referred to generally as "net beds" which term where appropriate is to be considered broadly to include a flexible web of any form, i.e. not necessarily mesh or net form although this is normally preferred.
Net beds are in general use as attachments for existing hospital beds, comprising support framework with four spaced support crutches for the rotatable shafts which can normally be lifted out of the crutches so as to hang down at the sides of the bed. In U.S. Pat. No. 4,270,234 there is disclosed such a net bed arrangement with a collapsible framework which is universal, in the sense that it can be used with almost any existing bed without the addition of special fittings or adaptors and even without the employment of tools.
With existing beds it is possible for the framework to be damaged if a shaft is not lifted "cleanly" out of its two support stirrups. When it is engaged only at one end, as may happen when lifted with one hand, it functions as a lever which enables very considerable and damaging twisting moments to be applied to the stirrup with which it is still engaged, and this can seriously damage and distort the framework.